Constant boiling mixtures of 1-chloro-2,2,2-trifluoroethane and hydrocarbons

ABSTRACT

Constant boiling mixtures of 1-chloro-2,2,2-trifluoroethane and certain hydrocarbons are useful as refrigerants, heat transfer media, gaseous dielectrics, expansion agents, aerosol propellants, working fluids in a power cycle and solvents.

BACKGROUND OF THE INVENTION

This invention relates to constant boiling binary mixtures of1-chloro-2,2,2-trifluoroethane and certain hydrocarbons. Such mixturesare especially useful as compression refrigerants, particularly insystems using centrifugal or rotary compressors.

The refrigerant capacity per volume pumped of a refrigerant is largely afunction of boiling point, the lower boiling refrigerants generallyoffering the greater capacity at a given evaporator temperature. Thisfactor to a great extent influences the design of refrigerationequipment and affects capacity, power requirements, size and cost of theunit. Another improtant factor related to boiling point of therefrigerant is minimum cooling temperature desired during therefrigeration cycle, the lower boiling refrigerants being used toachieve the lower refrigeration temperatures. For these reasons, a largenumber of refrigerants of different boiling temperature and capacity arerequired to permit flexibility of design and the art is continuallyfaced with the problem of providing new refrigerants as the need arisesfor new capacities and types of installations.

The lower aliphatic hydrocarbons when substituted by fluorine andchlorine are well-known to have potential as refrigerants. Many of thesefluoro-chloro hydrocarbons exhibit certain desired properties includinglower toxicity and nonflammability which have resulted in extensive useof such compounds in a large number of refrigeration applications.Trichlorofluoromethane and dichlorodifluoromethane are two of the mostcommonly available chlorine-fluorine hydrocarbon refrigerants availabletoday. There is a recognized need for refrigerants with boiling pointtemperatures between the relatively high boiling point temperature oftrichlorofluoromethane, plus 23.78° C. at atmospheric pressure, and therelatively low boiling point temperature of dichlorodifluoromethane,minus 29.8° C. at atmospheric pressure, in order to have availablerefrigerants of good performance in varying capacities.

Several fluoro-chloro hydrocarbons have boiling points in this range butsuffer from other deficiencies such as flammability, poor stability orpoor thermodynamic performance. Some examples of these types ofrefrigerants are tetrafluorodichloroethane, fluorodichloromethane,difluorochloroethane and fluorochloromethane.

It would also be possible to achieve the desired boiling point by mixingtwo refrigerants with boiling points above and below the desired one. Inthis case, for example, mixtures of trichlorofluoromethane anddichlorodifluoromethane could be used. It is well known, however, thatsimple mixtures create problems in design and operation because ofsegregation of the components in the liquid and vapor phases. Thisproblem is particularly troublesome in systems using centrifugalcompression because of the large quantities of liquid usually found inthe evaporator.

To avoid such segregation problems, the art is continually searching fornew azeotropic or constant boiling blends such as the constant boilingfluorocarbon blends disclosed in U.S. Pat. Nos. 3,607,755; 3,470,101;3,640,869; 3,505,232 and 3,634,255, or the constant boiling blends offluorocarbons and hydrocarbons disclosed in U.S. Pat. No. 3,249,546;U.S. Pat. No. 3,431,211 Canadian Pat. No. 829,259 and Soap and ChemicalSpecialties, August 1964.

An object of the present invention is to provide new constant boilingbinary mixtures with boiling points between that oftrichlorofluoromethane and dichlorodifluoroethane suitable for use asrefrigerants.

More particularly, it is an object of the present invention to providerefrigerant systems with a capacity between the refrigeration capacityof trichlorofluoromethane and dichlorodifluoroethane and which areuseful as compression refrigerants, particularly in systems using acentrifugal or rotary compressor.

Another object is to provide new, low boiling azeotropic or constantboiling mixtures which are useful in producing refrigeration in thosesystems in which cooling is achieved by evaporation in the vicinity ofthe body to be cooled and in which because of the nature of the system,the problem of segregation is critical.

DESCRIPTION OF THE INVENTION

In accordance with the present invention constant boiling mixtures havebeen discovered which consist essentially of1-chloro-2,2,2-trifluoroethane and a hydrocarbon selected from the groupconsisting of isopentane n-pentane, n-butane, isobutane and2,2-dimethylpropane. The compositions are as follows:

                                      TABLE I                                     __________________________________________________________________________    Mixture                                                                            Component A                                                                              Component B                                                                           Boiling Point                                         No.  (mole %)*  (mole %)*                                                                             (760 mm Hg)                                           __________________________________________________________________________    1    1-chloro-2,2,2-                                                               trifluoroethane (88)                                                                     isopentane (12)                                                                       4                                                     2    1-chloro-2,2,2-                                                               trifluoroethane (96)                                                                     n-pentane (4)                                                                         5                                                     3    1-chloro-2,2,2-                                                               trifluoroethane (39)                                                                     n-butane (61)                                                                         -5                                                    4    1-chloro-2,2,2-                                                                          2,2-dimethyl-                                                      trifluoroethane (55)                                                                     propane (45)                                                                          1                                                     5    1-chloro-2,2,2-                                                               trifluoroethane                                                                          isobutane                                                                             <-13° C.                                       __________________________________________________________________________     *at 20° C.                                                        

For the purpose of this discussion, by azeotropic or constant boiling isintended to mean also essentially azeotropic or essentially constantboiling. In other words, included within the meaning of these terms arenot only the true azeotrope described above at 20.0° C, but also othercompositions containing the same components in different proportionswhich are true azeotropes at other temperatures and pressures, as wellas those equivalent compositions which are part of the same azeotropicsystem and are azeotrope-like in their properties. As is well recognizedin this art, there is a range of compositions containing the samecomponents as the azeotrope, which, not only will exhibit essentiallyequivalent properties for refrigeration and other applications, butwhich will exhibit essentially equivalent properties to the trueazeotropic composition in terms of constant boiling characteristics ortendency not to fractionate upon boiling.

The novel azeotropic composition of the invention all have boilingpoints lower than that of their individual components. From theproperties of the components alone, the reduction in the boiling pointtemperature and azeotropic characteristics in the mixtures are notexpected.

The novel azeotropic mixtures provide increased refrigeration capacityover the components and represent new refrigeration mixtures especiallyuseful in systems using centrifugal and rotary compressors. The use ofthe azeotropic mixtures eliminate the problem of segregation andhandling in the operation of the system because of the behavior ofazeotropic mixtures essentially as a single component. The novelazeotropic mixtures are substantially non-flammable.

EXAMPLE 1

The azeotropes were determined in the following manner. Phase studieswere made wherein the composition of the various binary mixtures werevaried and the vapor pressures were measured at a temperature of 20.0°C. In all cases azeotropic compositions at 20° C were obtained at themaximum pressure as reported in the above Table. The azeotrope of1-chloro-2,2,2-trifluoroethane and isobutane was verified but itsprecise composition was not determined.

All the azeotropes have boiling points lower than the individualcomponents and thus affords higher refrigeration capacity for theazeotropes than the individual components and new refrigerating capacitylevels.

An evaluation of the refrigeration properties of the1-chloro-2,2,2-trifluoroethane/isopentane azeotrope of the invention andits fluorocarbon component is shown in the following Table. Isopentanealone is not suitable as a refrigerant in view of its flammability.

                                      TABLE II                                    __________________________________________________________________________    Comparison of Refrigeration Performance                                                            Azeotropic Composition                                                        Consisting of 88 mole %                                             1-Chloro-2,2,2-                                                                         1-chloro-2,2,2-trifluoroethane                                      trifluoroethane                                                                         and 12 mole % isopentane                                 __________________________________________________________________________    Evaporator 13.75     14.34                                                    Pressure, psia                                                                Condenser  53.35     54.36                                                    Pressure, psia                                                                Evaporator 40        40                                                       Temperature, ° F                                                       Condenser  110       110                                                      Temperature, ° F                                                       Discharge  116       110                                                      Temperature, ° F                                                       Net Refrigera-                                                                           69.9      72.78                                                    tion Effect (NRE),                                                            BTU/lb                                                                        Coefficient of                                                                           6.13      6.04                                                     Performance                                                                   (COP)                                                                         Displacement                                                                             9.02      8.64                                                     ft.sup.3 /minute/ton                                                          Compression                                                                              3.88      3.79                                                     Ratio                                                                         __________________________________________________________________________

By net refrigeration effect (NRE) is intended to mean the change inenthalpy of the refrigerant in the evaporator or, in other words, theheat removed by the refrigerant in the evaporator.

By coefficient of performance (COP) is intended to mean the ratio of theNRE to the compressor work. It is a measure of the efficiency of therefrigerant.

The azeotrope exhibits a 4.4% increase in capacity over1-chloro-2,2,2-trifluoroethane.

Additives such as lubricants, corrosion inhibiters and others may beadded to the novel compositions of the invention for a variety ofpurposes provided they do not have an adverse influence on thecompositions for their intended applications.

In addition to refrigerant applications, the novel constant compositionsof the invention are also useful as heat transfer media, gaseousdielectrics, expansion agents such as for polyolefins and polyurethanes,working fluids in power cycles, solvents and as aerosol propellantswhich may be particularly environmentally acceptable.

We claim:
 1. Constant boiling mixtures consisting essentially of 1-chloro-2,2,2-trifluoroethane and a hydrocarbon selected from the group consisting of isopentane, n-pentane, n-butane, 2,2-dimethylpropane and isobutane.
 2. Constant boiling mixtures according to claim 1 in which the hydrocarbon is isopentane and which boil at about 4° C. at 760 mm.
 3. Constant boiling mixtures according to claim 1 in which the hydrocarbon is n-pentane and which boil at about 5° C. at 760 mm.
 4. Constant boiling mixtures according to claim 1 in which the hydrocarbon is n-butane and which boil at about =5° C. at 760 mm.
 5. Constant boiling mixtures according to claim 1 in which the hydrocarbon is 2,2-dimethylpropane and which boil at about 1° C at 760 mm.
 6. Constant boiling mixtures according to claim 1 in which the hydrocarbon is isobutane and which boil under -13° C. at 760 mm.
 7. The process of producing refrigeration which comprises condensing a constant boiling mixture as described in claim 1 and thereafter evaporating said mixture in the vicinity of a body to be cooled.
 8. The process of claim 7 in which the constant boiling mixture condensed and evaporated is as defined in claim
 2. 9. The process of claim 7 in which the constant boiling mixture condensed and evaporated is as defined in claim
 3. 10. The process of claim 7 in which the constant boiling mixture condensed and evaporated is as defined in claim
 4. 11. The process of claim 7 in which the constant boiling mixture condensed and evaporated is as defined in claim
 5. 12. The process of claim 7 in which the constant boiling mixture condensed and evaporated is as defined in claim
 6. 